.Coincidentally, I noticed exactly this phenom using the ef24mm f/1.4L ii last weekend. The room was decorated for Christmas with those icicle lights hanging from the ceiling.

After reading this thread, I wonder if it is not the lens at all, but a different issue of light. When you look directly at any light bulb, it has some light source element inside and an outer casing (glass or plastic). Light passing directly from the source to your eye (or lens) passes through a minimal amount of the casing. Light at the sides or border is passing through substantially more casing material and is greatly diffused.

Anyway, just a thought; could be completely looney. But if there is some "fault" in optics, I want to lean toward the maker of the cheap light bulb rather than a team of optics engineers who designed and built a very expensive camera lens.

Krob97-my photo with the onion effect was not adjusted in photoshop or lightroom either. I don't mind the lemon effect as my 85mm has some of this as well. It is more that central target in the middle of the onion that I will have to decide if I can accept or not. My onion effect looks much more prominent than the other pictures I have seen. Other than this the lens looks great with only some mild softness at the edges till close to 2.8. Since I will be using it wide open much of the time that does not bother me.

Krob97-my photo with the onion effect was not adjusted in photoshop or lightroom either. I don't mind the lemon effect as my 85mm has some of this as well. It is more that central target in the middle of the onion that I will have to decide if I can accept or not. My onion effect looks much more prominent than the other pictures I have seen. Other than this the lens looks great with only some mild softness at the edges till close to 2.8. Since I will be using it wide open much of the time that does not bother me.

Gotcha! I don't mind the lemon effect either... all in all, there's nothing terrible here. Most folks looking at our images never seem to notice any of the slight defects that we the photogs seem to pick up instantaneously..

Seems like we can fret and fret over little abnormalities and oddities in our images and they can walk up behind you and say; "oh that's awesome!", "I love that shot". It's kind of crazy! My customers often seem to most like the photos that I like the least!

It's more prominent with smaller light sources when the focus distance is close and the light sources are also close, but still OOF.

True, and I inadventently had a nice 'test lab' this year since our tree had both clear miniature lights and the larger old skool solid color c4 lights. The mini - which as far as light sources goes is both the visible filament and the reflection of the filament in the clear glass - has some onion effect while the larger uniform light source c4 bulbs are perfectly smooth. Moral to the story is string your tree with c4 bulbs next year for premium quality bokeh, lol.